1. Field of the Invention
The invention relates to an optical magnification adjustment system and a projection exposure device.
2. Related Art
The photolithography method has been applied widely in various fields, in which a prescribed pattern is photographically imprinted by an exposure device on the surface of a substrate coated with photosensitive materials such as the photo resist, thereafter the pattern is formed on the substrate by etching process. Printed circuit boards are fabricated also by the exposure device in recent years. With a demand for more and more high-speed, multi-functional, and miniaturized electronics devices, the printed circuit boards are also required to be more and more multi-layered, dense, and microscopic.
Especially for building a multi-layered printed circuit board, an ultra-high precision is required in aligning a pattern on each layer with another when exposing the patterns.
In the tendency of the further miniaturization and multi-layering of printed circuit boards as mentioned above, the expansion and contraction of the board itself due to the difference between the expansion coefficients of the copper foil and the epoxy resin composing the printed circuit board can no longer be ignored.
It is an object of the present invention to provide an optical magnification adjustment system and a projection exposure device, that are capable of adjusting the magnification for projecting an image according to the expansion or contraction of a printed circuit board.
The preferred embodiment of the optical magnification adjustment system of the present invention has two lensesxe2x80x94the first lens, being plano-convex or plano-concave and having an optical power of xcfx862 as defined by the equation below, and the second lens being concave-plano or convex-plano and having an optical power of xcfx863 as defined by the equation belowxe2x80x94installed in a telecentric position on the side of the object surface to be projected or on the side of the projected image in the optical exposure system, and is capable of minutely adjusting the total system magnification of said optical exposure system.
xcfx863=xe2x88x92"PHgr"(S1+e1)/d0
xcfx862=("PHgr"xe2x88x92xcfx863)/(1xe2x88x92d0xcfx863)
where,
"PHgr": Optical power of the optical magnification adjustment system,
S1: Distance from the first surface of the first lens to the surface of an object 5 (photo mask surface),
d0: Center space between the two lenses, that satisfies the magnification xcex2=1, and
e1=t1/n1 (where, t1: the center thickness of the first lens, n1: refractive index of the first lens)
By the system configuration described above, the magnification xcex2 may be adjusted by increasing or decreasing the center space between the two lenses centering around d0, and therefore the magnification of the optical exposure system may be minutely corrected for high-precision enlargement or reduction of the projected image.
Further, with parallel planes of the same thickness as the total center thicknesses of said two lenses being inserted, it is desired to have the optical aberrations of said optical exposure system corrected in advance in accordance with its purpose.
By making said two lenses cylindrical, it is also possible to correct the magnification only in one direction of the image, either longitudinally or laterally, by adjusting the center space d in the same way as above.
In order to make achromatic condition, it is desired to set the Abbe numbers "ugr"1 and "ugr"2 of said two lenses in that the following equation will be satisfied.
"ugr"1/"ugr"2≈xcfx862/xcfx863